1. Field of the Invention
The present invention relates to compounds of the formula: ##STR1## as further defined herein. The compounds are useful as cardiotonic and vasodilating agents and as inhibitors of phosphodiesterase fraction III and platelet aggregation. In addition, the compounds are active as smooth muscle relaxants and bronchodilators. The present invention further relates to intermediates of these compounds as further defined herein.
2. Description of the Prior Art
Quinoline substituted pyridazin-3-ones have been shown to be cardiotonic agents and platelet aggregation inhibitors. Published European Patent Application No. 155,798 and British Patent No. 2,031,404 describe compounds of the formula: ##STR2## where R.sub.1, R.sub.2 and R.sub.3 may be H or lower alkyl.
U.S. Pat. No. 4,562,190 describes benzothiazole substituted pyridazin-3-ones of the formula ##STR3## where R.sub.1 is C.sub.1 -C.sub.6 alkyl and R.sub.2 is H, C.sub.1 -C.sub.6 alkyl or aryl.